The invention relates to the treatment of tobacco in general, and more particularly to improvements in methods and apparatus for transforming tobacco leaves into shreds which are ready for processing in cigarette makers and like machines. Still more particularly, the invention relates to the treatment of tobacco which, after harvesting, is stored in the form of bales or similar accumulations of compressed smokable material.
After harvesting, tobacco is normally subjected to a pronounced drying action so that its moisture content is reduced to between 9 and 10%. Dried tobacco is thereupon compressed into hogsheads, bales, packs or like accumulations (hereinafter called bales) of densely compacted smokable material. The bales can constitute blocks, cylinders or otherwise configurated bodies of densely compacted tobacco leaf laminae and/or ribs. If the leaves are destalked prior to drying, the ribs are gathered into discrete bales or like accumulations, or are admixed to destalked leaves (leaf laminae) after drying but prior to transformation into bales. A bale of tobacco leaf laminae and/or tobacco ribs can be stored for extended periods of time.
When the relatively dry material of a bale is to be converted into fillers of cigarettes or other smokers' products, the bales are broken up into loose leaf laminae and/or ribs prior to admission into a shredding machine in which the laminae and/or ribs are shredded preparatory to further treatment (heating or drying, mixing and/or the application of flavoring agents) in a cigarette maker or another machine. Since the constituents of the bales are rather dry (as mentioned above, their moisture content is between 9 and 10%) and strongly compressed, it is necessary to treat the bales gently in order to avoid unnecessary fragmentizing prior to admission into the shredding machine.
The presently preferred procedure of breaking up bales or similar accumulations of tobacco leaf laminae and/or ribs into their constituents includes the introduction of bales into a vacuum chamber and the utilization of one or more sharp probes or other suitable injectors which serve to admit steam whereby the steam tends to escape from the interior of the bale in the vacuum chamber and thereby heats and moisturizes the compacted material. Such heating and moisturizing enhances the suppleness of the particles and promotes their separation from one another. The just discussed mode of breaking up bales of tobacco particles is disclosed in U.S. Pat. No. 3,372,703. A drawback of such procedure that the apparatus for breaking up bales is bulky, compact and expensive and that its energy requirements are quite high.
The breaking up of bales into their constituents necessitates an increase of the moisture content from 9-10% to approximately 12-14%. In the next step, the loosened particles are moisturized again so that their moisture content rises to 18-23% in the case of leaf laminae and up to 30% in the case of ribs (these are considered to be the optimum moisture contents of laminae and ribs for shredding).
A modern shredding machine (reference may be had, for example, to commonly owned U.S. Pat. No. 4,172,515 granted Oct. 30, 1979 to Wochnowski) comprises two mutually inclined endless chain conveyors defining a compression chamber which tapers toward a mouthpiece and wherein the compressed particles of tobacco advance in the form of a so-called cake into the range of orbiting knives on a rotary drum-shaped carrier. The knives cooperate with the mouthpiece to convert the particles into shreds. The shreds are thereupon subjected to a drying action so that their moisture content is reduced to between 12 and 13.5% which is considered to be an ideal or a highly satisfactory moisture content for further processing in a cigarette maker or the like.
Repeated pronounced or less pronounced moisturizing and drying prior and/or after shredding contributes to space and energy requirements of such conventional apparatus and to their initial and maintenance cost.
U.S. Pat. No. 4,600,024 granted July 15, 1986 to Edwards proposes to replace the aforediscussed vacuum chamber and steam-discharging probes with an apparatus wherein bales of compressed tobacco particles are acted upon by microwaves which weaken the bonds between neighboring particles as a result of heating. The material of loosened bales is thereupon moisturized so that, in the opinion of men familiar with the art, its moisture content is best suited for shredding. The freshly formed shreds must be dried because their moisture content is much higher than that which is required for treatment in a cigarette maker or the like. Thus, this technique also involves the consumption of substantial amounts of energy, primarily as a result of moisturizing prior to shredding and as a result of drying upon completion of the shredding step.